The present invention relates to a bonding method of mounting and bonding a chip to a board such as a display panel.
A chip for a driver is mounted on a board such as a display panel. This mounting work is conducted in such a manner that the chip is mounted at a chip mounting position of an edge portion of the board via adhesive, and this chip is pressed to the board so that it can be bonded. Recently, in order to enhance the production efficiency, there is provided a bonding device capable of simultaneously conducting the bonding work on a plurality of boards at each station of bonding.
For example, in the case of a bonding device in which the chip is fixed by ACF (anisotropic conductive film), a plurality of working heads are provided in the ACF bonding stage in which an ACF tape is bonded to the edge portion of the board, in the provisional pressure-bonding stage in which the chip is mounted on this ACF tape and provisionally pressure-bonded and in the final pressure-bonding stage in which ACF is hardened and fixed when heat and a load are given to the chip provisionally bonded by pressure. The same work is conducted in parallel by the plurality of working heads on the plurality of boards.
In this device, the board is positioned by the centering step before the board is conveyed into the bonding device. Therefore, the plurality of boards are conveyed into the working stage under the condition that the relative positions of the plurality of boards are accurately adjusted. In each working stage, these boards are held on the same board support table, and these boards are recognized under this condition so that the positions are detected. When the board support table is moved according to the result of positional detection, the plurality of boards are positioned with respect to the working heads by the same positioning motion.
However, in the conventional bonding method in which the bonding device having a plurality of working heads is used, positions of the boards deviate, and the following problems may be encountered. As described above, it is presupposed that the relative positions of the boards are accurately adjusted by centering conducted before the boards are conveyed into the working stage. However, the relative positions of all boards are not necessarily accurately adjusted at all times. In some cases, the boards are conveyed into the working stage while the positions are deviating from predetermined positions for some reasons.
In this case, concerning one board, it can be accurately positioned to the working head when the board is positioned according to the result of positional detection obtained by recognition. However, concerning the other boards, due to the aforementioned positional deviation, it is impossible to accurately conduct positioning by the same positioning motion.
In the conventional bonding method, the position of each board is detected at each working stage. In the case where a positional deviation is caused as a result of the detection and the relative position exceeds an allowable range, a worker is obliged to stop operation of the device and manually correct the position. Therefore, each time the positional deviation occurs, it is necessary to stop the device and manually correct the relative position, which deteriorates the production efficiency.